Heretofore, steroids, immuran, and the like have been used for the treatment of various autoimmune diseases caused by unusual acceleration of immune activity in immunocompetent cells such as T cells. Although these drugs have considerable therapeutic effects upon certain diseases, they have side-effects such as adrenal insufficiency and leukopenia against normal cells. Therefore, more excellent drugs are still in demand.
The present inventors have found that fibroblasts and lymphocytes of animals produce a substance which regulates the DNA synthesis of immunocompetent cells such as T cells and that the substance regulates the activity of immunocompetent cells and is useful for the treatment of autoimmune diseases. Thus the present invention has been completed
Regulatory substances against immunocompetent cells have been reported in J. Immunol 109, 154-163 (1972), J. Immunol 116, 1452-1458 (1976) and Inflammation 1, 5-21 (1975). Since these known substances are high molecular substances, they have possibility of bringing about side-effects such as immuno-refusal effect of patients. The substance of the present invention is low molecular peptide derived from mammals and therfore, is expected to produce less side-effect and to be applicable to immuno-diseases.